Looking at the compatibility list (which seems to apply BOTH to the current Photo 10 and the new Photo RAW - is this an error on On1's support page?), it doesn't seem to support the latest Fuji X-Trans III sensors (the 16 MP Fujis are there, but not the 24 MP X-Pro 2 and X-T2). Interestingly, and I only noticed this because "Apple" is very close to the beginning of the alphabet and wound up on Page 1 of their list, they support the ancient (~1994) Apple QuickTake models (but NOT raw from the iPhone 7)...
The list may just be not quite up to date, because the X-Pro 2 and X-T2 are not the only recent cameras missing - the Pentax K-1 and Nikon D500 and D5 are missing as well - I really can't imagine them releasing without the Nikons and even the Pentax, since they are all standard Bayer cameras (the Nikons in particular are professionally important), and On1 already understands their header info (etc.) since they support .NEF and .PEF from other cameras. The 24 MP X-Trans is a bit more of a hassle, but an important one, since those are popular cameras whose owners are looking for better conversion.
What worries me about a list that includes the ancient QuickTakes, but not recent, relatively popular cameras, is that it suggests that this is an off-the-shelf RAW engine from somewhere (unless it's a mistake, and On1 Photo 10 is an off-the-shelf RAW engine, but Photo RAW is custom). NO ONE would develop for the QuickTakes today - where would you ever find one??? I am not at all sure that I don't personally own more X-Trans III cameras (two - one each X-Pro 2 and X-T2) than there are QuickTakes in the world in daily use today (the number in really active use could easily be 0 or 1, given that they are 0.3 MP cameras that require an Apple Serial connection that disappeared on the Blue & White Power Mac G3 in 1999). dcraw is known to support the old QuickTakes (and a number of other extremely obscure formats that On1 also picks up - ARRIRAW, for example, which only shows up in $50,000 movie cameras), raising the question "is this just an expensive front end to dcraw?". Further suggesting that it is dcraw based, the compatibility list has a bunch of odd notes about "hacked" cameras and the like, which are identical to the similar notes in dcraw's compatibility list.
The current dcraw list does include the newer cameras (not the X-T2, but the X-Pro 2 and the Nikons and Pentax), suggesting that On1 will pick them up in short order.
Could the image quality be the improvement they're claiming, if it's dcraw? Wouldn't any converter based on the same engine be pretty similar, at least in basic demosaicing (they could certainly differ in later adjustments to the file)? Maybe I'm unusually sensitive to demosaicing as a Fuji shooter, since Lightroom used to do an "interesting" job of it and still isn't perfect... I tried to find out how good or bad dcraw is at demosaicing Fuji files, but couldn't find any real info...